Trencher-scraper machine

ABSTRACT

A method and apparatus for excavating earth with a vehicle having a wheel or endless chain to which is secured a plurality of excavation elements such as buckets or blades which excavate earth and also provide propulsion for the vehicle. The wheel or chain is supported from the vehicle frame so that the lowermost of the excavation elements engages and bites into the surface of the earth. The wheel or chain is driven in a direction which advances the vehicle forwardly with excavation elements providing the primary source of traction. The vehicle also includes a scraper blade which is located behind the wheel or chain. The leading edge of the scraper blade advances with the vehicle and cuts into the earth below the level of the excavation wheel chain to slice off a further layer of earth. The scraper blade, additionally, serves as a braking element to resist any tendency of the excavating wheel or chain to ride upwardly out of the excavated channel. The force of the excavated earth acting on the advancing scraper blade cooperates with the weight of the vehicle to maintain the excavating wheel or chain in the excavated channel. The vehicle is assisted by a powered tractor which is employed to provide any supplemental traction necessary to overcome any resistance presented by the earth to the advancing blade which cannot be overcome by the traction of the excavating wheel or chain alone. As the vehicle advances the excavation elements fill with earth and are moved along an endless path to a conveyor which receives the earth and transports it away from the vehicle. The excavation elements remove continually a substantial portion of the upper layer of earth and the scraper blade excavates the remaining portion of the earth.

Peterson Sept. 12, 1972 [54} TRENCHER-SCRAPER MACHINE [72] Inventor:Carl Peterson, Boxford, Mass.

[73] Assignee: Foster-Miller Associates, Inc., Waltham, Mass.

[22] Filed: Jan. 16, 1970 [21] Appl. No.: 3,354

[52] US. Cl. ..37/90, 37/97, 37/108 R, 37/190, 37/192 R, 37/195 [51]Int. Cl. ..E02f 3/08, E02f 3/18 [58] Field of Search ..37/9, 8, 108,189-192, 37/90, 97; 172/785, 122, 123

[56] References Cited UNITED STATES PATENTS 2,088,369 7/1937 Flynn..37/190 X 84,230 11/1868 Stowell ..37/190 3,314,175 4/1967 Petty et a1..37/190 X 2,763,941 9/ 1956 Earley ..37/ 192 R X 1,985,188 12/1934Miller ..37/9 3,316,664 5/ 1967 Wilmoth et a1. ..37/9 3,224,120 12/ 1965Wilmoth et al. ..37/ 190 X 3,059,714 10/1962 Johnson ..37/8 UX 2,320,8556/1943 Dukes ..37/DIG. 20 1,231,352 6/1917 Hickman, Jr. ..172/122 X1,246,524 11/1917 Bager ..37/94 2,709,312 5/1955 Seifert ..37/1902,896,342 7/1959 Reising ..37/97 969,187 9/1910 Poulter ..37/862,068,433 1/ 1937 Peterson ..172/785 X 854,894 5/1907 Jones ..172/785FOREIGN PATENTS OR APPLICATIONS 137,833 10/1956 U.S.S.R. ..37/190116,210 2/1958 U.S.S.R. ..37/9

Primary Examiner- Robert E. Pulfrey Assistant Examiner-Clifford D.Crowder Attorney-Wolf, Greenfield, l-lieken & Sacks [5 7] ABSTRACT v Amethod and apparatus for excavating earth with a vehicle having a wheelor endless chain to which is secured a plurality of excavation elementssuch as buckets or blades which excavate earth and also providepropulsion for the vehicle. The wheel or chain is supported from thevehicle frame so that the lowermost of the excavation elements engagesand bites into the surface of the earth. The wheel or chain is driven ina direction which advances the vehicle forwardly with excavationelements providing the primary source of traction. The vehicle alsoincludes a scraper blade which is located behind the wheel or chain. Theleading edge of the scraper blade advances with the vehicle and cutsinto the earth below the level of the excavation wheel chain to sliceoff a further,

layer of earth. The scraper blade, additionally, serves as a brakingelement to resist any tendency of the excavating wheel or chain to rideupwardly out of the excavated channel. The force of the excavated earthacting on the advancing scraper blade cooperates with the weight of thevehicle to maintain the excavating wheel or chain in the excavatedchannel. The vehicle is assisted by a powered tractor which is employedto provide any supplemental traction necessary to overcome anyresistance presented by the earth to the advancing blade which cannot beovercome by the traction of the excavating wheel or chain alone. As thevehicle advances the excavation elements fill with earth and are movedalong an endless path to a conveyor which receives the earth andtransports it away from the vehicle. The excavation elements removecontinually a substantial portion of the upper layer of earth and thescraper blade excavates the remaining portion of the earth.

17 Claims, 16 Drawing Figures PATENTEHsEP 12 I972 sax-1U 1 or 3 INVENTORCARL R. PETERSON ATTORNEYS mtminsrm m2 3.690.023

saw a or 3 FIG. 4

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1 INVENTOR CARL R PETERSON 2/654 ywjwm m ATTORNEYS PATENYEDSEM m23.690.023

sum 3 or a Y aw a i 142" i FIG. 7

" lNVENTOR CARL R. PETERSON #Sadm ATTORNEYS 1 TRENCHER-SCRAPER MACHINEBACKGROUND OF THE INVENTION A number of machines have been proposed inthe prior art for excavating earth. Among the more common of machinesadapted to excavate large volumes of earth is a vehicle having a scraperblade which digs into the earth to slice off a layer of earth as thevehicle is driven forwardly. These machines are advanced along theearths surface by high powered tractors or bulldozers which mustgenerate sufficient force and traction to draw the scraper blade throughthe earth. Additionally, because of the large forces required to forcethe scraper blade through" the earth nearly all of the machinecomponents must be of massive construction in order to withstand thehigh loads which are developed. The requirement for high poweredtractors or bulldozers to advance the scraper is necessitated by therelatively crude excavating technique which simply scrapes off asubstantial thickness of the earths surface.

In order to overcome the disadvantages of scraper-- excavators,somemachines have been provided with rotary digging elements which millthrough the earths surface to excavate the earth. These rotaryexcavators are advanced forwardly along the earths surface by tractorsor bulldozers in much the same manner as the scraper-excavators referredto above. Additionally, these rotary excavators are rotated in adirection which tends to retard the forward advancement of the vehicle(the digging elements move forwardly through the earths surface duringexcavation). This presents substantial resistance to forward advancementof the vehicle. Because of the resistance to forward movement of thevehicle, high power tractors and bulldozers still are required.

Other excavating machines frequently include a bowl which receives theexcavated earth directly from the scraper blade or rotary excavator. Inmost instances, the earth is pushed upwardly into the bowl through anopening formed in its bottom as the vehicle is advanced by the separatepropelling unit such as a tractor. Such vehicles present a number ofdifficulties in that as the bowl fills up, a considerable and increasingresistance is presented to forward propulsion of the vehicle in that theearth must be loaded into the bowl from the bottom in opposition to theweight of the earth already in the bowl. In order to overcome this, someof these vehicles have been equipped with elevating devices to lift theearth and convey the earth to a location above the bowl from which it isdumped into the bowl. These elevators, however, serve no other functionand do not aid in propelling the vehicle. The layer of earth isexcavated off solely by the action of the scraper blade or rotaryexcavator. This limits the depth to which the blade may penetrate and,therefore, the thickness of the layer of earth which is removed. In theprior machines the thickness of the removed layer is dependent solely onthe traction between the tractor and the earth. Additionally, thethickness of layer which these devices may remove also is limited by thespeed of the elevator which transports the earth from the blade to theselfcontained bowl in the vehicle. Thus, even when the vehicle isassisted by supplemental tractors or bulldozers, its capacity is limitedby the operational speed of the elevator.

Prior vehicles which include self-contained storage bowls and theelevators described above, essentially are a compromise between ahauling vehicle and an excavation vehicle. This necessarily detractsfrom the efficiency of the vehicle while performing either of itsfunctions. For example, the size of the storage bowl and, therefore, thecapacity of the vehicle as a truck is limited because the truck alsomust include the relatively bulky and heavy elevator. When used as atruck, the elevator serves no purpose and provides undesirable deadweight.

A further disadvantage of prior excavating machines resides in theirbulky and heavy construction which is required to withstand the largeforces which develop during the. excavating operation. Because of theirheavy, bulky nature it is difficult to transport these machines from oneconstruction site to another. Additionally, the heavy weight of thesemachines has been necessary in order to provide proper traction betweenthe tractors and the earths surface and also to maintain the scraperblade or other digging device at its desired depth in the earthssurface. The instant invention overcomes these disadvantages byemploying a technique in which the excavating unit provides its owntraction and in which the forces transmitted to the frame of the machineare minimized thus enabling the frame to be of less bulky construction.

SUMMARY OF THE INVENTION inherent in currently available and known earthexcavators. In brief, the vehicle includes novel construction forexcavating the earth which may be employed in a combined excavator-truckor, as preferred, in a vehicle used only for excavating which conveysthe excavated material to a separate hauling truck which may remove theexcavated earth from the site.

In one embodiment of the invention, the vehicle includes a frame whichis pulled by a tractor and which supports a rotary excavator having aplurality of excavating elements, such as buckets, secured about itsperiphery. The frame is arranged to support the rotary excavator so thatits buckets will project below the surface of the earth and will biteinto the earth. Means are provided for controlling and adjusting thedepth of penetration of the buckets into the earth. A scraper blade alsois supported by the frame and is disposed just rearwardly of the rotaryexcavator to excavate further and scrape smoothly the earths surfacebehind the excavator. In contrast to prior rotary excavators, theinstant excavator is driven in a direction which will tend to advancethe vehicle forwardly instead of retarding forward movement. As theexcavation buckets of the rotary excavator bite into the earth theyloosen the earth and also provide substantial traction which propels thevehicle forwardly. The buckets which have penetrated the earth sliprearwardly as the vehicle advances, but still generate the necessarytractive force.

The traction provided by the rotary excavator is can trolled by varyingthe height of the excavator while maintaining the depth of the scraperblade constant. The traction of the excavator wheel is sufficient sothat the excavator wheel will provide a substantial horizontal advancingforce to propel the vehicle forwardly. In

addition, the excavating wheel may provide some of the force necessaryto advance the scraper blade in a forward direction. The remaining forcenecessary to overcome the resistance of the earth presented to thescraper blade is provided by the tractor. The excavator wheel thusremoves a substantial portion of the earths surface, so thatv thescraper blade only removes the remaining portion of the earths surface.Because the scraper blade does not remove the full layer of earth, theresistance of the earth to the scraper blade is less than inconventional machines. The propelling force which the tractor thus mustgenerate is considerably less than the force required by tractors andbulldozers on conventional machines in which the full layer is excavatedby the scraper blade.

As the vehicle advances forwardly the rotary excavator is drivencontinually so that earth trapped in its buckets or blades may betransported to a conveyor on the vehicle. The conveyor receives theexcavated earth as it empties from the buckets and transports theexcavated earth to a separate truck which moves alongside the excavatingvehicle. This technique enables the excavating vehicle and truck to beused to their full capacity in a more efficient manner than a combinedtruck-excavator. Additionally, the construction employed in thisexcavating machine enables a relatively thick layer of earth to beremoved with each pass of the vehicle thus affording a more economicaloperation as well as overcoming the difficulties presented in priormachines.

In another embodiment of the invention the excavating device may consistof an endless chain which is supported from the frame of the vehiclewith the excavating buckets being secured to the chain. The chain isarranged to provide the same function as the rotary excavator describedabove in that the buckets penetrate into the earth to provide tractionand to loosen the soil and thereafter to transport the soil to aconveyor which delivers the soil away from the excavating vehicle. Thisembodiment also includes a scraper blade which is supported behind thechain and which smoothes out the excavated surface behind the chain. Thechain arrangement is preferred in very large vehicles in lieu of therotary excavator which, in such vehicles, necessarily would be ofextreme dimensions. A chain excavator of the same capacity can bemounted within a smaller space than the rotary conveyor.

An additional feature of the invention resides in the arrangement bywhich the excavator is supported from the frame of the machine whichpermits the excavator to be raised or lowered thus varying the depth towhich its buckets or blades penetrate the earth. In addition tocontrolling the depth of penetration and, therefore, the thickness oflayer removed by the excavator wheel or chain, the control mechanism forvarying the height of the excavator also serves to control the balanceof traction between the excavation elements and the tractor.

It is among the primary objects of the invention to provide anexcavating machine in which the excavating member serves also to providepropulsion for the machine.

Also among the objects of the invention is to provide an excavatingmachine including a scraper blade in which a minimum of power isrequired to advance the scraper blade through the surface of the earth.

A further object of the invention is to provide an excavating machinehaving an excavating member and a scraper blade in which the excavatingmember removes a first portion of the earths surface while advancing ina direction tending to propel the vehicle forwardly and in which thescraper blade follows to remove the remaining layer of the earthssurface.

Still another object of the invention is to provide an excavatingmachine including a scraper blade in which a horizontal propelling forceis required to advance the scraper blade through the earth is minimized.

It is another object of the invention to provide an excavator whichremoves a layer of earth and conveys the removed earth to a locationremote from the excavator.

It is a further object of the invention to provide an excavating machinewhich is capable of removing relatively thick layers of earth from theground surface.

Yet another object of the invention isto provide an excavating vehiclewhich may remove large or thick layers of earth without requiring theassistance of supplemental high powered tractors or other drivemechanisms.

An additional object of the invention is to provide an excavatingmachine including a scraper adapted to scrape and smoothen the excavatedsurface and in which the earth to be scraped off initially is loosenedbefore engagement thereof by the scraper to present less resistance tothe scraper. The pre-softening of the soil also enables the excavatingmachine to be used in connection with relatively hardened earth whichnormally would present considerable resistance to advancement of aconventional scraping and excavating arrangement.

DESCRIPTION OF. THE DRAWINGS These and other objects and advantages ofthe invention will be apparent more fully from the following detaileddescription thereof with reference to the accompanying drawings wherein:

FIG. 1 is a somewhat schematic elevation of excavating machinesconstructed in accordance with the invention;

FIG. 2 is a plan view of the machine shown in FIG. 1;

FIG. 3 is a side elevation of a modification of the excavating machinein which the rear transport wheelsmay be varied in height;

FIG. 4 is a somewhat diagrammatic end view of the excavating machineillustrating the manner in which it may be employed to excavate a smoothhorizontal surface on a hill or slope; I

FIG. 5 is an exploded view of a connection between a tractor and themain frame of the excavating machine;

FIG. 6 is an elevation of a modification of the excavator including anendless chain excavator unit;

FIG. 7 is a section through the endless chain excavator unit as viewedfrom the plane 7-7 of FIG. 6;

FIG. 8 is a side elevation of the scraper blade having projectionssecured thereto;

FIG. 9 is a sectional plan view of the scraper shown in FIG. 8 as viewedalong the line 9-9 of FIG. 8;

FIG. 10 is a schematic illustration of the clearance between the rotaryexcavator and its associated scraper blade;

FIG. 11 is an illustration similar to that of FIG. 10 in which thescraper blade in contoured to parallel the locus of motion of the rotaryexcavator unit;

FIG. 12 is a schematic elevation similar to that of FIG. 11 in which thescraper blade is contoured tobe disposed in parallel to the locus ofadjustment of the chain excavator;

FIG. 13 is a somewhat diagrammatic elevation of a modified scraper bladehaving forwardly projecting fingers;

FIG. 14 is a somewhat diagrammatic plan view of the structure shown inFIG. 13;

FIG. 15 is a'diagrammatic elevation of the machine with a modifiedconveyor; and

FIG. 16 is a plan view of the machine shown in FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the machine,shown in FIGS. 1 and 2, includes a main frame consisting of a pair ofoverhead longitudinal rails 12 and rearward downwardly depending framesections 14. Two or more trailing wheels 16 are rotatably mounted to therear frame section 14 as by the axle l8-and may be powered or freelyrotatable. The forward ends of the overhead rails 12 are pivoted to theframe of a tractor 22 about a vertical axis such as at the vertical pin24 to facilitate steering. The vehicle is controlled by the operator whois located in the cab 26 atop the tractor. The tractor also, of course,includes an engine 28 which powers the vehicle.

The vehicle includes an excavation unit, indicated generally by thereference character 30, which is supported from the overhead rails 12 ofthe main frame. As shown in FIGS. 1 and 2 the excavation unit includes aplurality of rotary excavation wheels 32 which are arranged generally inlateral, spaced alignment with each other. Each of the excavation wheels32 includes a plurality of buckets 34 secured circumferentially aboutthe wheels 32. Each of the wheels 32 is driven, as described below inmore detail, in a direction which will advance the vehicle forwardly (tothe left as seen in FIG. 1). The buckets 34 are arranged about theirassociated wheels 32 so that as the wheels 32 are rotated (counterclockwise as seen in FIG. 1) the open faces of the buckets 34 will diginto, loosen and become filled with the earth but maintain traction onthe soil. The traction thus obtained enables the excavation wheels 32 tobe employed for driving the vehicle forwardly as well as to aid in theexcavation process.

The excavation wheels 32 cooperate with a scraper blade 36 having aleading edge 38 which extends transversely of the vehicle. The scraperblade 36 is arranged in relation to the excavation wheels 32 so that itsleading edge 38 penetrates into the earth to a greater depth than thatof the buckets 34. Means are provided for adjusting the relative depthto which the excavation wheels 32 and scraper blade 36 penetrate theearth, and consequently, the relative thickness of the earths layerwhich is excavated by the excavation wheel and scraper blade. Theheightwise adjustment capability of the excavation wheel 32 in relationto the scraper blade 36 also provides means for controlling the tractionand forward propulsion of the machine while maintaining the blade 36 ata constant desired penetration level. The heightwise position of theexcavation wheel 32 controls the balance of tractive effort which isdeveloped by the tractor and the excavation wheel 32.

penetrates the earth. As the excavator wheel is raised the tractor willbear more of the vehicle weight and, therefore, can develop moretraction. Under optimum operating conditions, the tractive forcegenerated by the tractor is enough only to overcome the drag of thescraper blade 36, the remaining forward propulsion being generated bythe excavator wheel 32. Because the scraper blade 36 cuts through athinner layer of earth than prior machines excavating to the same depth,the forward tractive propulsion generated by the tractor need not be asgreat as the propulsion which normally would be required. This avoidsthe use of supplemental bulldozers or multiple tractors, as in the priorart. Thus, in operating the machine, the depth of penetration of thescraper blade 36 is set to the desired excavation depth. The height ofthe excavation wheels 32 then are adjusted to a level at which they willprovide sufficient horizontal forward traction which will permittheztractor to supply the remaining horizontal force necessary toovercome the drag and resistance of the earth to the scraper blade 36.As the machine advances, the power of the tractor may be varied by theoperator to overcome obstacles such as rocks, stumps, ets.

As the excavation wheels 32 rotate, they tend continually to riseupwardly and out of the excavated channel. The excavation wheels 32 aremaintained in the channel by the weight of the vehicle and also by theaction of the scraper blade 36 which tends to wedge into the earth, thusimparting a downwardly directed component of force to the frame of themachine through the scraper blade. The magnitude of this force isdependent on a number of factors such as the location of the scraperblade with respect to the excavation wheels, the characteristics of theearth being excavated, the extent to which the excavation wheels haveloosened the soil through which the excavation blade passes and theangle at which the leading edge 38 of the 'blade 36 meets the earth. Thescraper blade also provides a reaction surface against which theexcavation wheels 32 may load or throw any earth which they have notscooped up in the buckets. Additionally, the scraper blade 36 assistssubstantially the excavation operation and finally smoothes out theexcavated surface left behind. The relative portions of the excavatedlayer which are removed by the excavating wheels and the blades may bevaried as the height of the excavating wheel 32 is varied, In someinstances, the excavating wheel may project only half way through theintended excavation depth with the excavating blade 36 being positionedat the full depth. Under other operating conditions, the excavationwheel 32' will be spaced more closely to the excavation blade. Becausethe scraper blade 36 digs into soil which has been loosened somewhat bythe excavation wheels 32, the resistance which the earth presents to thescraper blade 36. as it advances may vary. Both the excavation wheels 32and the scraper blade 36 are supported from the frame 10 for heightwiseadjustment to control the depth of cut as well as for retracting theseunits upwardly out of the way when the vehicle is used on the road orhighway.

In the embodiment shown in FIGS. 1 and 2 each of the excavation wheels32 is supported on a wheel frame 40, each wheel frame 40 having a numberof supporting rollers 42 joumaled at spaced locations about the wheelframe 40. The rollers 42 on each wheel frame 40 engage the innercylindrical surfaces 44 of their associated excavation wheel 32 tosupport and guide the excavation wheels 32 for rotation about a fixedtransverse axis. Each of the wheel frames 40 is arranged in transversealignment so that the respective excavation wheels 32 also will bearranged in transverse alignment. The wheel frames 40 are secured to andsupported by a transverse frame 46 which extends transversely across thevehicle and through each of the excavation wheels 32.

The transverse frame 46 and wheel frames 40 are suspended from theoverhead rails 12 of the main frame by laterally spaced pivot arms 48which embrace the overhead rails 12 and which are pivoted at one end tothe lateral ends of pins fastened to the frame 10. The pivot arms 48extend rearwardly and downwardly from the pins 20 toward he transverseframe 46 to which the pivot arms 48 are rigidly fastened.

The rearward end of the excavation unit 30 is supported by a pair offluid operated cylinders 50 which are pivoted to the overhead rails 12and which have downwardly extending piston rods 52 which are pivoted, attheir lower ends, to the transverse frame 46. In addition to supportingthe excavation unit, the arrangement of pivot arms 48 and fluidcylinders 50 permit the height of the excavation wheels 32 to becontrolled by the operator. The fluid operated cylinders 50 may beactuated to swing the excavation unit and pivot arms 48 about the pivot20 to the desired heightwise position. As shown in FIG. 2 the'overheadrails 12 may be disposed along the space between adjacent excavationwheels 32 so that when raised to their uppermost position the excavationwheels 32 project upwardly through and beyond the overhead rails 12.

When raising or lowering the excavation wheels 32 it may be necessary toraise or lower the scraper 36 therewith. As shown, the scraper isfastened to a slide 54 which, in turn, slides along a guiding surface 56formed on the rear frame section 14. The heightwise movement of theslide 54 and scraper 36 along the guiding surface 56 is controlled byfluid operated cylinders 58 which are pivoted at one end to the overheadlongitudinal rails 12 and which have downwardly extending piston rods 60which are connected to the slide 54. Thus, by controlling the cylinders50 and 58 the height of both the excavation wheels 32 and scraper 36 maybe controlled relative to the frame of the vehicle and relative to eachother.

A number of arrangements may be provided for driving the excavationwheels 32. A suggested arrangement is shown in the drawings and includesa number of gear teeth 62 arranged circumferentially about the lateralsurfaces of each of the excavation wheels 32. The teeth 62 are enmeshedwith pinion gears 64 which are rotatably mounted to the wheel frame 40.Each of the pinion gears is driven by achain 66 which, in turn, isdriven by a driving gear; 68.Each driving gear 68 is fastened to atransversely extending excavator drive shaft which is powered by theindependent motors 72. The laterally outward chains 66 and associatedgears 64, 68 may be contained within the hollow pivot arms 48. The shaft70 is journaled, at its ends, to the pivot arms and the motors 72 aresecured to the pivot arms and connected to the shaft 70. The motors 72may be controlled by the operator to regulate the rotary speed of theexcavation wheels 32.

The invention also includes an arrangement for transporting theexcavated earth from the buckets 34 to a location remote from theexcavation vehicle such as to a hauling truck to transport the excavatedearth to a different location. For this purpose, the excavator includesa conveyor supported on the transverse frame 46 and which extendsthrough and transversely of the excavation wheels 32. The conveyorindicated generally by reference character 74 protrudes laterally andoutwardly of the ends of the most lateral excavation wheels 32. Theconveyor 74 may be of generally conventional design having a pluralityof rollers 76 which support and guide a flexible conveyor belt 78. Theconveyor 74 may be driven in either direction and preferably is drivenby a reversible motor. During operation as the excavation wheels 32rotate, the earthfilled buckets 34 are rotated to a position above theconveyor 74. When in this position the buckets 34 begin to emptydownwardly with the earth falling onto the conveyor. The conveyorpreferably is provided with receiving plates 80 which extend along andon either side of the conveyor to collect all of the earth falling fromthe buckets 34 as they discharge. The conveyor then transports the earthlaterally toward and away from the machine.

In a modified version of the excavating vehicle, it

may be preferable to eliminate the sliding, movable 1 construction ofthe scraper blade 36 and secure the scraper blade 36 directly to theframe in order to transmit more effectively the forces between thescraper blade and the main frame.

FIG. 3 shows a modification of the vehicle in which the scraper blade36' is fastened rigidly to the main frame. The excavation wheels 32 aremounted and supported from the frame in the same manner as in theembodiment as shown in FIG. 1. In this embodiment, the scraper blade 36is raised and lowered in unison with the main frame to which it isattached. This action is provided by mounting the trailing wheels 16 toconnecting links 84 which are pivoted to the rear frame section 86 atthe pin 88. The pivotal position of the connecting links 84 iscontrolled by a pair of fluid operated cylinders 90 which are pivoted attheir upper ends to the upper portion of the rear frame section 86 andwhich have piston rods 92 pivotally connected at the pins 94 to theouter end of the connecting links 84. The cylinders 90 are controllableto pivot the wheels 16 from the position shown in solid in FIG. 3 to theposition shown in phantom and indicated generally by the referencecharacter 96. In operation, the cylinder 90 is operated to control theheight of the frame 10 and, therefore, simultaneously control the levelof the scraper blade 36 and excavation wheels 32.

A further advantage of the arrangement is that by operating thecylinders 90, both the scraper blade 36 and excavation wheels 32 areraised or lowered simultaneously and in unison which avoids thenecessity of readjusting one of these parts relative to the other afterone of the parts has been shifted in position. The relative dispositionbetween the excavation wheels 32 and the blade may be controlledseparately by the fluid operated cylinder 50 which connects the mainframe to the transverse frame of the excavating unit in the same mannerdescribed above.

The cylinders 90 may be operated in unison or independently of eachother. This enables the wheels 16 to be maintained at the same or atdifferent elevations with respect to the frame 10. The advantage in thisarrangement is shown somewhat diagrammatically in FIG. 4 whichillustrates the vehicle as used to excavate and scrape a flat horizontalsurface on the side of a hill or other sloping terrain. As shown in FIG.4, the tractor 22 is driven along the side of the hill and is disposedin a position which is inclined to the vertical. The main frame,however, which follows the tractor is maintained in a generally verticalupright position so that the excavation unit 30 and scraper blade 36remain in a level, horizontal configuration. The main frame 10 ispivoted to the tractor about a longitudinal axis topermit such relativeangular orientation. The main frame is supported in this position bycontrolling the position of the wheels 16 by the fluid cylinders 90 sothat the uphill of the wheels 16 is raised in relation to the downhillof the wheels 16. As the vehicle advances forwardly it excavates aportion of the hillside and leaves the excavated portion flat andhorizontal. The vehicle advances along the hill in this configurationuntil the trailing wheels 16 advance to the flat and level excavatedportion. The cylinders 90 then are operated to return the wheels 16 tothe same horizontal position so that the excavation unit is maintainedin its generally vertical disposition as the wheels 16 then followbehind on the flat, excavated portion of the earth.

When the vehicle shown in FIG. 3 is transported along the road, thecylinders 90 are actuated to swing the wheels 16 downwardly fully to theposition shown in phantom at 96. This effectively raises the frame andexcavating unit above the road level to provide sufficient roadclearance for the frame and its supported parts. Additionally, thewheelbase of the vehicle is reduced which enhances somewhat themaneuverability on the road.

FIG. shows an exploded arrangement of the joint between the main frameand the tractor which permits the tractor 22 and frame 10 to be pivotedwith respect to each other about a vertical axis for steering, and abouta horizontally axis to enable the tractor and frame 10 to assumedifferent upright attitudes as when used on the sides of hills and thelike. The connection joint may include a vertical socket 98 formed inthe frame of the tractor 22. The socket 98 receives the lower pin 100 ofa T-shaped connector 102. The connector 102 also has a pair ofhorizontally extending pins 104 which intersect and are perpendicular tothe lower pin 100. The pins 104 are received within longitudinallyspaced bearing plates 106 which are secured to the forward end of themain frame 10. The pins 20, which support the pivot arms 48 are securedand extend laterally from the main frame 10 in the region of this swiveljoint.

A further embodiment of the invention is shown in FIGS. 6 and 7 and issubstantially identical to that described above except that the rotaryexcavation wheels 32 are replaced by endless excavation chains,indicated generally at 108. A number of such endless excavation chains108 are arranged in pairs transversely of the vehicle in the same manneras-the arrangement of excavation wheels 32 described above. Each of theexcavation chain pairs is supported by an L-shaped chain frame 110.Three sprockets 112,114, and 116 are rotatably mounted on the chainframe 10 at its free ends and at its bent portion, the excavation chains108 being wrapped endlessly about the sprockets 112, 114' and 116. Anumber of buckets 118 are secured to the outer periphery of each pair ofchains for the same purpose as the buckets 34 on the rotary excavationunit 30 described above. The buckets 118 preferable include a number offorwardly projecting teeth 120 and are arranged so that when the chains108 are driven in an excavating direction (counter clockwise as seen inFIG. 6) the lower of the buckets l 18 which are located along the bottomrun of the chains 108 face rearwardly to penetrate'through the soil andfill the buckets 118. The lower run of the chains 108 extends along thelower leg 122 of the L-shaped chain frame 110 and is defined by thatportion of the chain 108 which extends across the lower sprockets 1 14,l 16.

The. chain excavation unit is suspended from the chain frame 10 by apair of pivot arms 124 which are pivoted at their upper ends, to theoverhead rails 12 at the pins 126. The forwardlyand downwardly extendingends of the pivot arm 124 are pivoted to the forwardly extending end ofthe lower leg 122 of the L-shaped chain frame 110. The pivot arms.l24and the forward ends of the frame 110 and chain excavator unit areraised or lowered by a pair of fluid operated cylinders 128 which arepivoted to the overhead rails 12 of the frame at the pins 130 and whichhave downwardly extending piston rods 132 which are pivotally connectedto the forward lower ends of the pivot arms 124. The cylinders 128 areoperative to raise or lower the forward end of the chain frame 1 10.

The rearward end of the chain excavation unit is supported adjustably bya pair of fluid operated cylinders 134 which are pivotally connectedbetween the overhead rails 12 of the frame 10 and the upper portion ofthe chain frame 110 near the sprocket 114. The rear-- ward cylinders 134are adjusted primarily to control traction and depth of penetration ofthe chain excavator- The forward cylinders 128 are useful primarily toraise the forward end of the chain excavator above ground level when thevehicle is transported over the road. In some instances, however, it maynot be necessary to raise the forward end of the chain excavator andthecylinder 128 may be replaced with a rigid structural member. This,however, depends on the dimensions and particular structuralcharacteristics of the machine.

The drive for the excavator chain 108 preferably is taken from anindependent motor and is transmitted to the chain through the uppersprockets 112. The motor (not shown) may be secured to one of theL-shaped. ex.- cavator frames or to the transverse frame 136 whichextends across all of the chain frames 110 and secures the chain framesin registration with eachother. The

I 136 and operates in the same manner as the conveyor 74 described abovein connection with the rotary excavation unit 30.

FIG. 7 shows, in section, the pattern which the excavation chains 108 orexcavation wheels 32 make as they advance through the upper layer of theearth. This pattern consists of a number of parallel channels 150separated by earth walls 152. The buckets thus remove a substantialportion of the material to be excavated. The scraper blade 36, whichfollows the buckets, advances along the plane 154. The materialexcavated by the blade thus includes a lower layer of earth togetherwith the walls 152 and other earth not picked up by the buckets. Thethickness of the lower layer is, of course, dependent on the relativeheightwise setting between the excavation buckets and the leading edgeof the scraper blade 36. When the lower level is relatively thin, theresistance of the earth to the advancing edge of the scraper blade 36 isrelatively small. In addition, the resistance maybe reduced further ifthe earth has been loosened substantially by the excavating unit. Evenwhen the lower layer of earth presented to the scraper blade 36 isrelatively thick, however, this layer still is less thick than the layerwhich normally is presented to conventional scraping or excavatingmachines in which the scraper performs the primary excavating operation.In these prior machines, the resistance of the earth to the scraper isconsiderable. In contrast, the lower resistance presented to theadvancing scraper enables the use of a tractor with less power toadvance the vehicle. The power which the tractor must generate islessened further by reason of the traction generated by the excavationunit, which during optimum conditions of operation, generates asufficient tractive force to overcome at least a portion of the drag onthe scraper blade.

In each of the foregoing embodiments of the invention, the blades orbuckets excavate a number of parallel but closely spaced channels in theearth, the channels being separated by thin walls of earth. It is, ofcourse, desirable to fill the buckets completely for efficientexcavation. In order to insure that the buckets are filled completely,projections as shown in FIGS. 8 and 9 may be formed on the scraper blade36. The projections 156 preferably are arranged to be disposedalternately between the excavating wheels or chains to engage and urgethe unexcavated walls 152 sideways into the buckets. The projections maybe V-shaped either of symmetrical or unsymmetrical cross section orother contour designed to break down the earth walls and direct theearth laterally toward and into the buckets.

In some instances, a machine constructed in accordance with theinvention may be employed to excavate relatively deep trenches bypassing the machine over the excavated area a number of times. The depthof the trench may be such that the transverse conveyor 74 is disposedbelow the level of the earths surface, 166 as shown in FIG. 15, andcannot, by itself, carry the excavated earth to a remote location. Whenthe machine is used to excavate such relatively deep trenches theconveyor should be modified as shown in FIGS. 15 and 16 so that itdirects and transports the earth inwardly through the excavation units32to a central conveyor 168 which extends forwardly and then upwardlyabove the level of the earth's surface 166. The conveyor 168 may includea transversely extending portion 170 to remove the earth toa separatehauling vehicle. This technique may be modified to include any number offorwardly extending conveyors 168 disposed between adjacent selectedwheels 32 or excavation chains.

Each embodiment of the invention described thus far includes a mechanismwhich permits continuous relative heightwise adjustment of theexcavating unit in relation to the scraper blade 36 and also continuousheightwise adjustment of the excavation unit and scraper blade in unisonin relation to the frame and, therefore, the surface to be excavated.FIG. 10 shows, somewhat diagrammatically, the most simple of thearrangements between the excavating unit and its associated scraperblade in which a relatively large clearance is provided between the unitand its blade so that there will be no interference throughout the fullrange of relative movement between these parts. FIG. 11 shows anarrangement by which the scraper blade 36 is of a special shape whichparallels closely the locus defined by the excavator wheel 32 as it ismoved to various adjusted positions. F IG. 12 shows a similararrangement in which clearance is provided between the scraper blade andthe chain excavator. In this arrangement a contoured chain guide 162 isprovided between the sprockets 112, 114 to support and guide the run ofchain between the sprockets in a generally circular path about thesprocket 116. The scraper blade 36 is arranged in generally concentricrelation to the chain guard. The chain excavator is pivoted to a raisedor lowered position about the axis of the sprocket 116 to vary the depthof excavator penetration and scraper blade penetration.

Operation of the machine involves controlled cooperation between thetransport wheels 16, 23 and the chain or rotary excavation unit to varythe height of the excavation unit in relation to the frame and,therefore, in relation to the surface of the earth. As described above,the heightwise position of the excavation unit determines the balance ofweight distribution between the transport wheels 16, 23 and theexcavation unit, the optimum balance being determined in part by thecomposition and consistency of the earth being excavated. The heightwiseposition of the excavation unit may be varied between an upper positionin which the full weight of the vehicle is borne by the transport out ofthe excavated region. The balance shouldbe such that the primary forwardadvancing force of the vehicle is developed by the excavation unit withthe tractor wheels 23 providing supplemental assistance I only toovercome the drag ofthe scraper blade.

A very substantial excavating operation thus is performedv by thebuckets or other excavating elements which fill with earth and thentransport the earth to the conveyor which transports the excavated earthto a remote location. The excavating operation is finished by thefollowing scraper blade 36 which is disposed below the level excavatedby the excavation unit. The scraper blade acts as a brake in oppositionto the force of the excavation unit, providing a wall for the rotatingor advancing excavation elements to load against and also preventingrearward spillage of excavated earth. The blade also excavates furtherto smooth out the excavated surface left behind. Depending on thedigging action and penetration of the excavating elements, the scraperblade may advance through relatively loose soil which presents littleresistance to the advancing scraper blade. This is in direct contrast toprior excavators in which the advancing scraper blade digs directly intofirm, packed soil. Indeed, this is one of the limiting factors in suchprior devices which requires supplemental powered units such asbulldozers to provide the necessary driving force for the blade.

In some instances, it may be desirable to provide additional means forincreasing the downwardly directed force component of the machine toinsure further that the excavating unit does not tend to climb forwardlyout of the excavated channel. Any tendency for the excavator unit toclimb out of its channel will tend to raise the'wheels 23 of the tractor22, thus reducing the tractive effort of the wheels 23 and possibly evenraising the wheels 23 completely off the ground. A further hold-downforce may be generated by modifying the scraper blade, as shown in FIGS.13 and 14, to include a number of forwardly extending fingers 162 whichproject forwardly from the edge of the scraper blade. The fingers 162are spaced laterally of the scraper blade and are disposed betweenadjacent excavator wheels 32 or excavator chain pairs 108. The forwardends of these projections extend into relatively firm soil which has notyet been loosened substantially by the advancing buckets of theexcavating unit. Additionally, the forward ends 164 of these projectionsare formed in a wedge-like incline so that their advancement willgenerate a downwardly directed force to the blade and the frame to whichthe blade is secured. The wedge surface 164 may be relatively shallow ormay extend over a considerable area. By generating downwardly directedforces in response to advancement of the unit instead of merely holdingthe unit down by the bulk weight of the machine a more efficient andlighter machine may be produced.

Thus, I have provided an improved method and apparatus for excavatingthe surface of the earth which eliminates the relatively large thrustheretofore required with conventional scraping excavators. Moreover,these objectives are achieved by the use of a forwardly rotatingexcavating unit which both excavates and provides tractive force. Theexcavation unit cooperates with a scraper blade which brakes theopposing force of the excavation unit, provides a wall for the reverserotation excavating unit .to load against and, in addition, furtherexcavates and smoothens out the region left behind.

The heightwise positions of the excavation unit and scraper blade areadjustable in unison and with respect to eachother to permit the balanceof traction between the excavation unit and the tractor to becontrolled; The technique and apparatus avoids the necessity forsupplemental power such as other bulldozers or tractors to overcome theheretofore 'high resistance of the earthto the scraper unit.

It should be understood that the foregoing description of my inventionis intended merely to be illustrative thereof and that other embodimentsand modifications will be apparent tothose skilled in theart withoutdeparting from its spirit. For example, although the invention has beendescribed primarily as employed in a the machine intended forexcavationalone it may be incorporated into a combinedexcavating-hauling 'vehicle, if desired. Although such a combinationtends to reduce the general efficiency of the machine as an excavatingunit because it necessarily is a compromise between a hauling andexcavating vehicle, the excavating function of the vehicle is moreefficient than currently available and known combined excavation-haulingvehicles. Further modifications may relate to the arrangement forheightwise movement on the frame. Additionally, although the transportmeans has been illustrated as comprising regular road wheels, chain-likeendless tracks could be substituted although such tracks would not be assuitable for road use.

Having thus described the invention, what I desire to claimand secure byLetters Patent is:

l. A surface excavating machine comprising: a main frame, transportmeans for enabling saidframe to advance along the earths surface,excavating means including a plurality of excavating elements supportedon said frame for movement along an endless path, means mounting saidexcavating means on said frame to enable a portion of said endless pathto' intersect the surface of the earth when said vehicle is disposed onsaid surface to cause said excavating elements to penetrate the earthssurface to a selected depth at which said elements may provide tractionalong the earths surface; drive means for moving said excavatingelements in endless sequence along said endless path and in a directionwhich tends to advance said machine'forwardly when said excavatingelements are in engagement with the earth s surface; said excavatingelements being so constructed and arranged as to entrap a volume ofearth and thereafter carry said volume of earth along said endless pathto a location remote from said ex.- cavated surface to enable saidentrapped volume of earth to be discharged from saidexcavating elements;and blade means supported by said mainframe, for engaging andpenetrating the earths surface below the penetration depth. of saidexcavating means, said blade means being mounted tosaid frameand beingconstructed to present a forwardly and downwardly inclined surface tothe earth thereby to generate a downwardly directed force in response toforward advancement of said machine thereby maintaining said excavatingmeans in continuous penetrating relation to the surface of the earth andprecluding said excavating means from 5 climbing out of the excavatedregion.

2. An apparatus as defined in claim 1 wherein the weight of said machineis distributed between said transport means and said excavating means,said apparatus further comprising:

means mounting said excavating means to said frame for adjustablemovement heightwise of said frame, said transport means and said blademeans whereby the weight borne by said excavating means may be varied tocontrol the balance of traction between said excavating means and saidtransport means to preclude said excavating means from climbingforwardly out of the excavated region.

3. An apparatus as defined in claim 2 wherein said blade means furthercomprises:

a scraper blade mounted to said frame rearwardly of said excavating unitand having a blade edge disposed below the level of said excavatingunit.

4. An apparatus as defined in claim 3 wherein said transport meansincludes powered tractor means connect'ed to said frame for assisting inforward advancement of the machine.

5. An apparatus as defined in claim 3 wherein said scraper blade isdisposed in proximity to the excavating means toprovide a reactionsurface for earth thrown rearwardly by said excavation means to assistin self m ntsloading of said excavation means and to provide said 12. Anapparatus as defined in claim 11 wherein said hold-down force as saidmachine advances forwardly. 3 finger means includes reaction surfacesdisposed at an 6. An apparatus as defined in claim 3 wherein said angleto the direction of advancement of said blade scraper blade is mountedfor heightwise adjustable means to increase further the downwardlydirected movement on said frame whereby the excavation depth componentof force generated by said blade means. of said scraper blade and thedownwardly directed 13. An apparatus as defined in claim 1 furthercomforce generated thereby may be controlled simultaneprising: ously.conveyor means mounted. to said frame to receive 7. An apparatus asdefined in claim 6 wherein said earth discharged from said excavatingelements, scraper blade and said excavation means are mounted saidconveyor means extending transversely for heightwise adjustment inunison and in relation to through the center of said machine andthereafter 10. An apparatus as defined in claim 1 further comprising:

a plurality of said excavating means mounted in a gang in transverselyspaced relation on said frame and in substantially transverse registry;

each of said excavating means being rotatably supported about a supportframe, each of said support frames being secured to a transverse frameextending transversely of the main frame of said machine, saidtransverse frame being supported from said main frame of said machine;

said blade means having a blade edge disposed rearwardly of and belowthe level of said gang of said excavating means to excavate anadditional layer of earth and to smoothen the excavated surface leftbehind; and

projection means secured to said blade means and extending forwardlybetween adjacent excavating means in said gang to divert earthtransversely toward and into the excavation elements on said excavationmeans.

11. An apparatus as defined in claim l.further comprising:

said blade means being mounted to said frame rearwardly of saidexcavating means and having a blade edge disposed below the level ofsaid excavating means, and

forwardly projecting finger means secured to said blade and extendingforwardly of said edge thereof to engage and loosen relatively firm soilwhich has not yet been engaged fully by said excavating eleeach other.extending upwardly whereby when said earth 8. An apparatus as defined inclaim 1 further comreceiving portion of said conveyor means is prising:disposed below the level of the earths surface said means mounting saidexcavating means to said frame for adjustable movement heightwise ofsaid frame and said transport means whereby the weight of said machineborne by said excavating means may be varied to vary the traction ofsaid excavating means said means mounting said excavation means for saidmovement comprising:

pivot arm means pivoted adjacent one end to said frame and having theother, free end thereof con nected to said excavation means; and

adjustable drive means operatively connecting said other end of saidpivot arm means to said frame to upwardly extending portion of saidconveyor means may transport said excavated earth to a location remotefrom said machine and out of said excavated region.

14. A method of excavating a surface layer of earth with an excavatingmachine comprising:

providing a plurality of excavating elements arranged in an endlesssequence which excavating elements are adapted to entrap a volume ofearth;

supporting a portion of the weight of said excavating machine bymobility means resting on said earths surface and being adapted topermit said machine ments, said conveyor means being adapted to receiveand transport discharged earth to a remote location.

raise and lower said free end of said arm. to advance and be transportedalong the earths 9. An apparatus as defined in claim 1 furthercomsurface; prising: advancing said endless series of excavatingelements conveyor means mounted to said frame to receive along anendless path to cause said excavating elesaid earth discharged from saidexcavating elements to dig into and to penetrate the earths surface,said penetration being effective both to provide traction for saidmachine and to fill said excavating units with earth;

controlling the balance of weight bearing on said excavating elementsand said mobility means thereby to control the traction of saidexcavating elements through said earth, said traction being controlledto advance said machine forwardly while excavating said earth entrappedwithin said excavation elements; and

engaging the earth with a blade means below the penetration depth ofsaid excavation elements and in a attitude which presents a forwardlyand downwardly inclined surface to the earth to generate a downwardlydirected force in addition to that caused by the weight of said machinein response to forward advancement of said machine.

15. A method as defined in claim 14 further comprismg:

locating said blade means in proximity to said excavation elements toassist self-loading of said excavation elements.

16. A method as defined in claim 15 wherein said step of controlling thebalance of weight borne by said transport means and said excavationmeans comprises:

varying the relative height between said excavation elements and saidmobility means.

17. A method of excavating earth from the earth's surface comprising:

positioning a scraper blade so as to provide a forwardly and downwardlyinclined surface in penetrating relation to the earths surface and at apredetermined penetration depth;

providing a plurality of excavating elements arranged in an endlesssequence, said excavating elements being adapted to entrap a volume ofearth;

locating said excavating elements in a position to penetrate the earth'ssurface in advance of said scraper blade and at a lesser penetrationdepth than said scraper blade, whereby said excavating elements andscraper blade may be advanced so providing a supplemental power tractionmeans connected to said machine for providing additional forwardtractive effort, said additional forward tractive effort being of amagnitude sufficient-to overcome the forward resistance of the earthpresented to the scraper blade which is not overcome by the forwardpropulsion of said excavating elements.

1. A surface excavating machine comprising: a main frame, transportmeans for enabling said frame to advance along the earth''s surface,excavating means including a plurality of excavating elements supportedon said frame for movement along an endless path, means mounting saidexcavating means on said frame to enable a portion of said endless pathto intersect the surface of the earth when said vehicle is disposed onsaid surface to cause said excavating elements to penetrate the earth''ssurface to a selected depth at which said elements may provide tractionalong the earth''s surface; drive means for moving said excavatingelements in endless sequence along said endless path and in a directionwhich tends to advance said machine forwardly when said excavatingelements are in engagement with the earth''s surface; said excavatingelements being so constructed and arranged as to entrap a volume ofearth and thereafter carry said volume of earth along said endless pathto a location remote from said excavated surface to enable saidentrapped volume of earth to be discharged from said excavatingelements; and blade means supported by said main frame, for engaging andpenetrating the earth''s surface below the penetration depth of saidexcavating means, said blade means being mounted to said frame and beingconstructed to present a forwardly and downwardly inclined surface tothe earth thereby to generate a downwardly directed force in response toforward advancement of said machine thereby maintaining said excavatingmeans in continuous penetrating relation to the surface of the earth andprecluding said excavating means from climbing out of the excavatedregion.
 2. An apparatus as defined in claim 1 wherein the weight of saidmachine is distributed between said transport means and said excavatingmeans, said apparatus further comprising: means mounting said excavatingmeans to said frame for adjustable movement heightwise of said frame,said transport means and said blade means whereby the weight borne bysaid excavating means may be varied to control the balance of tractionbetween said excavating means and said transport means to preclude saidexcavating means from climbing forwardly out of the excavated region. 3.An apparatus as defined in claim 2 wherein said blade means furthercomprises: a scraper blade mounted to said frame rearwardly of saidexcavating unit and having a blade edge disposed below the level of saidexcavating unit.
 4. An apparatus as defined in claim 3 wherein saidtransport means includes powered tractor means connected to said framefor assisting in forward advancement of the machine.
 5. An apparatus asdefined in claim 3 wherein said scraper blade is disposed in proximityto the excavating means to provide a reaction surface for earth thrownrearwardly by said excavation means to assist in self loading of saidexcavation means and to provide said hold-down force as said machineadvances forwardly.
 6. An apparatus as defined in claim 3 wherein saidscraper blade is mounted for heightwise adjustable movement on saidframe whereby the excavation depth of said scraper blade and thedownwardly directed force generated thereby may be controlledsimultaneously.
 7. An apparatus as defined in claim 6 wherein saidscraper blade and said excavation means are mounted for heightwiseadjustment in unison and in relation to each other.
 8. An apparatus asdefined in claim 1 further comprising: means mounting said excavatingmeans to said frame for adjustable movement heightwise of said frame andsaid transport means whereby the weight of said machine borne by saidexcavating means may be varied to vary the traction of said excavatingmeans said means mounting said excavation means for said movementcomprising: pivot arm Means pivoted adjacent one end to said frame andhaving the other, free end thereof connected to said excavation means;and adjustable drive means operatively connecting said other end of saidpivot arm means to said frame to raise and lower said free end of saidarm.
 9. An apparatus as defined in claim 1 further comprising: conveyormeans mounted to said frame to receive said earth discharged from saidexcavating elements, said conveyor means being adapted to receive andtransport discharged earth to a remote location.
 10. An apparatus asdefined in claim 1 further comprising: a plurality of said excavatingmeans mounted in a gang in transversely spaced relation on said frameand in substantially transverse registry; each of said excavating meansbeing rotatably supported about a support frame, each of said supportframes being secured to a transverse frame extending transversely of themain frame of said machine, said transverse frame being supported fromsaid main frame of said machine; said blade means having a blade edgedisposed rearwardly of and below the level of said gang of saidexcavating means to excavate an additional layer of earth and tosmoothen the excavated surface left behind; and projection means securedto said blade means and extending forwardly between adjacent excavatingmeans in said gang to divert earth transversely toward and into theexcavation elements on said excavation means.
 11. An apparatus asdefined in claim 1 further comprising: said blade means being mounted tosaid frame rearwardly of said excavating means and having a blade edgedisposed below the level of said excavating means, and forwardlyprojecting finger means secured to said blade and extending forwardly ofsaid edge thereof to engage and loosen relatively firm soil which hasnot yet been engaged fully by said excavating elements.
 12. An apparatusas defined in claim 11 wherein said finger means includes reactionsurfaces disposed at an angle to the direction of advancement of saidblade means to increase further the downwardly directed component offorce generated by said blade means.
 13. An apparatus as defined inclaim 1 further comprising: conveyor means mounted to said frame toreceive earth discharged from said excavating elements, said conveyormeans extending transversely through the center of said machine andthereafter extending upwardly whereby when said earth receiving portionof said conveyor means is disposed below the level of the earth''ssurface said upwardly extending portion of said conveyor means maytransport said excavated earth to a location remote from said machineand out of said excavated region.
 14. A method of excavating a surfacelayer of earth with an excavating machine comprising: providing aplurality of excavating elements arranged in an endless sequence whichexcavating elements are adapted to entrap a volume of earth; supportinga portion of the weight of said excavating machine by mobility meansresting on said earth''s surface and being adapted to permit saidmachine to advance and be transported along the earth''s surface;advancing said endless series of excavating elements along an endlesspath to cause said excavating elements to dig into and to penetrate theearth''s surface, said penetration being effective both to providetraction for said machine and to fill said excavating units with earth;controlling the balance of weight bearing on said excavating elementsand said mobility means thereby to control the traction of saidexcavating elements through said earth, said traction being controlledto advance said machine forwardly while excavating said earth entrappedwithin said excavation elements; and engaging the earth with a blademeans below the penetration depth of said excavation elements and in aattitude which presents a forwardly and downwardly inclined surface tothe earth to generate a downwardly directed force in addition to thatcaused by the weight of said machine in response to forward advancementof said machine.
 15. A method as defined in claim 14 further comprising:locating said blade means in proximity to said excavation elements toassist self-loading of said excavation elements.
 16. A method as definedin claim 15 wherein said step of controlling the balance of weight borneby said transport means and said excavation means comprises: varying therelative height between said excavation elements and said mobilitymeans.
 17. A method of excavating earth from the earth''s surfacecomprising: positioning a scraper blade so as to provide a forwardly anddownwardly inclined surface in penetrating relation to the earth''ssurface and at a predetermined penetration depth; providing a pluralityof excavating elements arranged in an endless sequence, said excavatingelements being adapted to entrap a volume of earth; locating saidexcavating elements in a position to penetrate the earth''s surface inadvance of said scraper blade and at a lesser penetration depth thansaid scraper blade, whereby said excavating elements and scraper blademay be advanced so that said excavating elements remove a first layer ofearth and said said scraper blade removes a second lower layer of earth;said blade also generating a downwardly directed force in response toforward advancement of the machine, advancing said endless series ofexcavating elements along an endless path to generate forward tractionfor said excavating elements and said scraper blade; providing asupplemental power traction means connected to said machine forproviding additional forward tractive effort, said additional forwardtractive effort being of a magnitude sufficient to overcome the forwardresistance of the earth presented to the scraper blade which is notovercome by the forward propulsion of said excavating elements.